Re: [MacPerl] comparing image files

["Jefferson R. Lowrey" <lowrey@mailbag.com>]

At 7:37 AM -0500 9/12/99, Greenblatt & Seay wrote:
>>Rich Morin wrote:
>>I don't think I can get away with comparing JPEG images, because
>>they are compressed.  OTOH, I feel sure that I can convince some
>>package (once I find it :-) to expand JPEGs into pixmaps.
>
>Would Chris Nandor's glue work on GraphicConverter (or some other graphic
>program) to have MacPerl open each JPEG and then 'save as' an uncompressed
>file? If not, I would think this could be done using MacPerl to issue
>KeyQuencer commands (via the KeyQuencer's Hypercard XCMD) to do that job.
>I've been able to automate many a mundane process using this powerful
>combination.

IIRC Graphic Converter is not 'scriptable'.  Clip2Gif is something that
comes up  a lot in the AS community when dealing with the problem of batch
converting files from one format to another.  DeBabelizer also does - but
that's buyware, and Clip2Gif (which should be more powerful than it's name
suggests) is some version of (share|free|postcard|beer|joke)ware.

>
>I have quite a few JPEGs that have white backgrounds with the image in the
>middle. An approach that tried to compare images by just looking at the
>corners would not be able to distinguish between these.

It's relatively easy to come up with pathological cases that break any
algorithm that doesn't look at the whole image.

-Jeff Lowrey



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